There are two types of traditional slave strobes. One is hard-wired (or controlled wirelessly in some examples) to the master device (usually a camera) and fires its strobe when the master signals it to do so. In this configuration, it could be controlled to fire multiple times and could even be told to fire for a particular length of time depending on the control signals received from the master device. One disadvantage for this type of slave strobe is that the master and the slave must be designed to work together, since they both must use the same set of control signals. This limits a family of slave strobes to a particular family of master devices that use the same control signals.
The other traditional slave strobe is one that “looks” for a short pulse of light that is significantly brighter than the ambient light. These slaves fire when they detect a strobe fire from a master device or even from a secondary slave device. This type of slave strobe is very convenient as it does not require a camera with a strobe output (many of the newer pocket cameras do not include a strobe output).
Many slave strobes are limited in their ability to operate in differing power modes, delay modes, and other modes of operation. Typically, a slave strobe will have a slide switch allowing a user to change power modes, however, these switches are typically small and fragile.
Often a slave strobe will have a set angle covered by the flash, and are unable to focus a flash for distant objects. If a user desires to change the color of a slave strobe, most strobes require a filter accessory to be placed in front of the flash tube containing a color filter. Alternatively, some of these strobe filter accessories have had the ability to contain fresnel lenses, and thus change the focus of the flash. However, such accessories are cumbersome, easy to lose or forget, and susceptible to damage.